# US 8,572,327 B2 · System and method of selectively caching information based on the interarrival time of requests for the same information

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- Number: US 8,572,327 B2
- Document ID: US8572327B2
- Status: Granted
- Kind: B2
- Application number: 13/213,779
- Filed: 2011-08-19
- Published: 2011-12-08
- Granted: 2013-10-29
- Earliest claimed: 2009-08-21
- Assignees: Google Inc.
- Applicants: Timo Burkard; David Presotto
- Inventors: Timo Burkard; David Presotto
- Web page: https://patentgrep.com/patent/US8572327B2

## CPC

- G06F 12/123: with age lists, e.g. queue, most recently used [MRU] list or least recently used [LRU] list
- G06F 12/00: Accessing, addressing or allocating within memory systems or architectures (digital input from, or digital output to record carriers, e.g. to disk storage units, G06F3/06)
- G06F 12/0246: {in block erasable memory, e.g. flash memory}
- G06F 12/0842: for multiprocessing or multitasking
- G06F 12/0888: using selective caching, e.g. bypass
- G06F 12/121: using replacement algorithms
- G06F 12/122: of the least frequently used [LFU] type, e.g. with individual count value
- H04L 67/5683: Storage of data provided by user terminals, i.e. reverse caching
- G06F 12/0871: Allocation or management of cache space
- G06F 2212/264: Remote server
- G06F 2212/7209: Validity control, e.g. using flags, time stamps or sequence numbers
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

A system and method is provided wherein, in one aspect, a currently-requested item of information is stored in a cache based on whether it has been previously requested and, if so, the time of the previous request. If the item has not been previously requested, it may not be stored in the cache. If the subject item has been previously requested, it may or may not be cached based on a comparison of durations, namely (1) the duration of time between the current request and the previous request for the subject item and (2) for each other item in the cache, the duration of time between the current request and the previous request for the other item. If the duration associated with the subject item is less than the duration of another item in the cache, the subject item may be stored in the cache.

## Claims

### Claim 1

A system comprising:
a processor configured to retrieve and store items in memory in accordance with instructions;
a first memory having a first capacity and a first access time, where access time refers to the average time it takes for the processor to obtain information from a memory;
a second memory having a second capacity and a second access time, the second capacity being greater than the first capacity and the second access time being slower than the first access time;
a third memory having a third capacity and a third access time, the third capacity being greater than the second capacity and the third access time being slower than the second access time;
the instructions comprising, in response to a request for a request for the item received by the processor:
determining whether the requested item was previously requested;
retrieving the requested item from first memory when the requested item is stored in the first memory;
retrieving the requested item from second memory when the requested item is stored in the second memory;
retrieving the requested item from third memory when the requested item is stored in the third memory;
storing the requested item in the first memory in response to (i) a determination that the requested item was previously requested and (ii) a first elapsed time since a most recent previous time the requested item was requested being less than a second elapsed time associated with access of another item stored in the first memory; and
storing the requested item in the second memory in response to a determination that the requested item was not previously requested or the first elapsed time is greater than the second elapsed time.

### Claim 2 (depends on 1)

The system of claim 1 wherein the first memory is a flash memory.

### Claim 3 (depends on 2)

The system of claim 2 wherein the second memory is a disk memory.

### Claim 4 (depends on 2)

The system of claim 2 wherein the processor accesses the third memory via a network.

### Claim 5 (depends on 1)

The system of claim 1 wherein the items of information comprise chunks of video files.